Medium frequency propagation: A survey

The propagation of ground waves and sky waves at medium frequencies is considered. Variations in daytime and nighttime propagation are discussed. Published ground wave propagation curves applying to land which is smooth and of uniform conductivity are discussed and method for calculating field strengths along mixed land-sea paths, over irregular terrain, and through built up areas are presented. Coupling losses occurring in sky wave propagation due to the existence of the gyromagnetic frequency band of the Earth within the medium frequency band are considered. Polarization coupling loss, which is of importance in tropical regions, and coupling loss between hops on multihop paths are discussed. Enhanced ionospheric cross modulation also occurs at the gyromagnetic frequency.